When a laser emits a laser beam, the beam inherently has a Gaussian intensity profile wherein the center portion of the beam is brighter than the outer edges of the beam. Sometimes the power intensity difference between the middle and the edges of the beam can be greater than ten percent. Further, when a laser beam emitted from a laser diode is passed through a fiber optic to direct the projection of the beam, the beam begins to spread throughout the fiber optic and spreads when the beam exits the fiber optic. When these two phenomena are observed in a single system, a laser beam emitting from a fiber optic coupled to a laser diode, the beam spreads out at an angle and has a Gaussian profile. FIGS. 1 and 2 illustrate this phenomena in detail, where a fiber optic 1 has a pair of light beams 10 and 11 exiting therefrom. The beams 10 and 11 bounce against the walls of fiber optic 1 until they exit an end potion. They will exit at a certain angle α from optic fiber 1. Angle α can vary from optic to optic depending on the width and straightness of the fiber and the propagation of the beam within the fiber.
As the light beams exit from fiber optic 1, they will generally have a greater concentration at the center of the projection path than at the edges. Thus, when the light beams are directed at a target, the illuminated portion will be brighter in the center than at the edges of the portion. This is the Gaussian profile. FIG. 2 illustrates this phenomenon graphically. The graph represents the light distribution along line A—A in FIG. 1. In the graph, the width distance of the light beams represents the horizontal axis and the power intensity of the beam is represented by the vertical axis. Note that the closer to the center of the light beam, the greater the concentration of individual light rays and hence more power. This will appear as a bright center tapering off to a dimmer outer portion of the light projection.
Prior art devices and apparatus have been devised to reduce these effects. For example, U.S. Pat. No. 5,148,317, incorporated by reference in its entirety, places a lens in the path of a laser beam. When the spreading laser beam enters the lens, the curvature of the lens collimates the light waves so they all travel through the lens in a parallel fashion. At the projection end of the lens, a diffractive optical pattern redirects the light waves to create an even illumination pattern on the projection target.
Another device places a homogenizer plate between the laser light source and a target plane, which is described in U.S. Pat. No. 6,025,938, incorporated by reference in its entirety. The homogenizer plate has a hologram pattern consisting of a series of diffractive fringes which direct the laser source to different portions of the target plane creating an even illumination and power intensity at the target plane.
Problems with these systems are that they require multiple pieces of equipment. In particular situations, such as space travel, where space is a large concern, such additional equipment can take up this space, and thus raise costs of a mission. Furthermore, it also performs unnecessary tasks by collimating the light throughout the lens, rendering the system greatly inefficient.